Are you on T Mobile? If so...the Sidekick I tried was some garbage...IMO. From the hardware button layout for the menu, phone, search, etc. to the software design.
After using Android since 2010...the Sidekick seemed like a step back. I would pick the Droid 1 over that. The software...its a strange mix of stock Android and something custom from Samsung. I would probably pick the older version of Blur on the Devour over whats on the Sidekick. And as bad as the one I tried lagged, I think it needed a custom ROM or something. I didnt even have it long enough to try a factory reset.
The G Nex in a landslide if I had to choose between the 2. Just based on software alone.